Add default flush calls to gpu backend.

Change-Id: I7cd8ff975502128dbde86397218b7e5c115cdaa6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/299141
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/RELEASE_NOTES.txt b/RELEASE_NOTES.txt
index 81e91ec..7f66cf9 100644
--- a/RELEASE_NOTES.txt
+++ b/RELEASE_NOTES.txt
@@ -6,6 +6,13 @@
 
 Milestone 86
 ------------
+  * Adds default flush() calls to SkSurface, SkImage, and GrContext. These calls do
+    a basic flush without a submit. If you haven't updated Skia in a couple release
+    and still have flush() calls in your code that you expect to do a flush and
+    submit, you should update all those to the previously added flushAndSubmit() calls
+    instead.
+    https://review.skia.org/299141
+
   * Enable BackendSemaphores for the Direct3D backend.
     https://review.skia.org/298752